Hybrid vehicle system

ABSTRACT

This system comprises an engine  1,  a transmission device  4,  a clutch  3  for engaging/disengaging the engine  1  with/from the transmission device  4,  a rotational electric device  2,  a power transmission mechanism  5  for inputting the rotation of the rotational electric device  2  to the transmission device, and an accumulator element  7  for accumulating electrical power supplied by the rotational electric device  2.  A control unit  20  determines a gear change instruction for the transmission device  4,  and if gear change instruction is determined, it disengages the clutch  3,  and controls the rotation of the rotational electric device  2  in such a manner that the rotational speed of the input shaft of the transmission device becomes a target rotational speed required for a gear changing operation.

TECHNICAL FIELD

This invention relates to a so-called parallel type hybrid systemwherein an engine and a rotational electric motor (motor generator) areprovided as power sources of a vehicle.

BACKGROUND ART

Japanese Patent Application No. H11-160759 discloses a parallel typehybrid system which comprises: an engine, a transmission device forchanging the speed of rotation of an input shaft and transmitting saidrotation to vehicle wheels via an output shaft, a clutch for engaging/disengaging the output shaft of the engine with/from the input shaft ofthe transmission device, a rotational electric device serving as anelectric motor and an electric generator, a power transmission mechanismfor coupling the input and output shafts of the rotational electricdevice with the input shaft of the transmission device, and anaccumulator element for accumulating electrical power supplied by therotational electric device.

In prior applications of this kind, it can be seen that the friction andinertia of the rotational electric device acts via the powertransmission mechanism on the input shaft of the transmission device,thereby placing a great load on the synchronous mechanism when changinggear, and increasing the gear changing time (synchronous time).

DISCLOSURE OF THE INVENTION

It is an object of the present invention to enable gear changingoperations to be carried out smoothly and rapidly in the transmissiondevice of a hybrid system.

The hybrid system for a vehicle according to the present inventioncomprises: an engine, a transmission device for gearing the speed ofrotation of an input shaft and transmitting said rotation to vehiclewheels via an output shaft, a clutch for engaging/disengaging the outputshaft of the engine with/from the input shaft of the transmissiondevice, a rotational electric device serving as an electric motor and anelectric generator, a power transmission mechanism for coupling theinput and output shafts of the rotational electric device with the inputshaft of the transmission device, and an accumulator element foraccumulating electrical power supplied by the rotational electricdevice. Moreover, it also comprises means for determining gear changeinstructions for the transmission device; means for disengaging a clutchwhen a gear change instruction is determined; and means for controllingthe rotation of said rotational electric device in such a manner thatthe rotational speed of the input shaft of the transmission deviceassumes a target rotational speed required for a gear changingoperation.

Consequently, according to the present invention, the rotational speedof the input shaft of the transmission device is made to converge to atarget rotational speed and rapidly come within the synchronizationrange of the target gear, by means of rotational control of therotational electric device, and hence the synchronous time can beshortened and the load on the synchronous mechanism can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system overview showing an embodiment of this invention.

FIG. 2 is an explanatory diagram of the operation of the aforementionedsystem.

FIG. 3 is an explanatory diagram of the operation of the aforementionedsystem.

FIG. 4 is an explanatory diagram of the operation of the aforementionedsystem.

FIG. 5 is an explanatory diagram of the operation of the aforementionedsystem.

FIG. 6 is an explanatory diagram of the operation of the aforementionedsystem.

FIG. 7 is an explanatory diagram of the operation of the aforementionedsystem.

FIG. 8 is a flowchart describing the control procedure in theaforementioned system.

FIG. 9 is a map showing the output distribution of an engine and motorin the aforementioned system.

FIG. 10 is a flowchart describing the control procedure in theaforementioned system.

FIG. 11 is a flowchart describing the control procedure in theaforementioned system.

BEST MODE FOR CARRYING OUT THE INVENTION

As shown in FIG. 1, the power train of a vehicle comprises: an engine 1,a transmission 4 (transmission device), and a clutch 3 interposedbetween the output shaft 12 (crank shaft) of the engine 1 and the inputshaft 41 of the transmission 4.

The output of the engine 1 is transmitted via the clutch 3 to the inputshaft 41 of the transmission 4, and during travel of the vehicle, it isfurther transmitted from the output shaft 42 of the transmission 4, viaa propeller shaft, differential gears, and drive shafts, to the left andright-hand wheels of the vehicle.

The engine 1 is constituted by a diesel engine or CNG engine (usingcompressed natural gas as a fuel). The output of the engine 1 iscontrolled by an electronic engine control unit (ECU) 10, as describedhereinafter.

The clutch 3 is caused to engage and disengage by a clutch actuator 31,and the transmission 4 performs gear changing by means of a gear shiftactuator 43 whilst the clutch 3 is engaged/disengaged, on the basis of agear change command from the operator, as described hereinafter. Thetransmission 4 is a transmission device with a clutch, which performs agear change operation by means of a gear shift actuator 43 on the basisof a gear change operation signal from a change lever unit 23 whichissues a gear position command corresponding to the position of a changelever for gear changing which is operated by the driver.

The power train of the vehicle further comprises a motor generator 2, apower transmission mechanism 5 for coupling the input and output shaft21 of the motor generator 2 with the input shaft 41 of the transmission4, and a motor clutch (second clutch) 60 for engaging/disengaging themotor generator 2 with the power transmission mechanism 5.

The motor generator 2 uses a permanent magnet type synchronous electricmotor (IPM synchronous motor). The motor generator 2 is connected to theaccumulator element 7 via an inverter 6.

The inverter 6 converts the stored electrical power (DC power) of theaccumulator element 7 into AC power and supplies it to the motorgenerator 2, which is driven as an electric motor. The inverter 6 alsoconverts power generated by the motor generator 2 (AC power) into DCpower and stores it in the accumulator element 7.

In the accumulator element 7, in order to generate braking energyefficiently and rapidly, without causing waste, an electric double-layercapacitor is used, which can readily guarantee the output densityrequired with respect to the tolerable weight of the vehicle battery.

The power transmission mechanism 5 is constituted by a drive gear 51coupled to the input/output shaft 21 of the motor generator 2, a drivengear 53 coupled to the input shaft 41 of the transmission 4, and an idlegear 52 which meshes with the aforementioned gears.

The output rotation of the motor generator 2 is geared down by means ofthe power transmission mechanism 5 and transmitted to the input shaft 41of the transmission 4. When the vehicle is regenerating energy, therotation of the input shaft 41 of the transmission 4 is geared up bymeans of the power transmission mechanism 5 and transmitted to the inputshaft 21 of the motor generator 2, thereby performing an electricalpower generating action.

A hybrid ECU 20 is provided in order to control the aforementionedclutch 3, transmission 4, inverter 6, engine ECU 10, and so on.

The hybrid ECU 20 is input with various signals from: the change leverunit 23 which generates a gear position command corresponding to theposition of the change lever for changing gear; an accelerator openingsensor 22 which detects the amount by which the accelerator pedal isdepressed (the accelerator demand amount); a brake sensor 26 whichdetects the amount by which the brake is operated (brake demand amount);a sensor 44 which detects the output revolution speed of thetransmission 4; a sensor 54 which detects the gear revolution speed inthe power transmission mechanism 5 (transmission 4 input revolutionspeed sensor); a clutch position sensor 29 which detectsengagement/disengagement of the clutch 3; and (although not illustratedin the drawings), a gear position sensor which detects the shiftposition of the transmission 4, and a meter which detects the storedcharge (SOC) of the accumulator element 7, and the like. Furthermore, itis also supplied with a detection signal from the engine revolutionsensor 13 which is input to the engine ECU 10.

The hybrid ECU 20 controls the clutch actuator 31, gear shift actuator43 and inverter 6 on the basis of the various signals described aboveand information signals from the engine ECU 10, and it also sends engineoutput request signals to the engine ECU 10.

Moreover, the hybrid ECU 20 and the engine ECU 10 are connected in abi-directional fashion by means of communications control means, in sucha manner that various types of co-operative control can be performed, asdescribed hereinafter.

The details of the control performed by the hybrid ECU 20 are nowdescribed.

When the vehicle is accelerating or running under the output of themotor generator 2 only, then it controls the inverter 6 in such a mannerthat an output corresponding to the operational amount of theaccelerator is obtained from the motor generator 2, in a state where theclutch 3 is disengaged. The output of the motor generator 2 istransmitted via the power transmission mechanism 5 to the input shaft 41of the transmission 4, as shown in FIG. 2, and the rotation istransmitted from the output shaft 42 of the transmission 4 to thepropeller shaft.

When the vehicle is traveling under the output of the engine 1 only,then an output request signal is sent to the engine ECU 10, and theoperation of the motor generator 2 is halted, in a state where theclutch 3 is engaged. The engine ECU 10 controls the amount of fuelsupplied to the engine 1 in such a manner that an output correspondingto the amount of operation of the accelerator is obtained, and thisoutput of the engine 1 is transmitted via the clutch 3 to the inputshaft 41 of the transmission 4, as shown in FIG. 3, and then from theoutput shaft 42 of the transmission 4 to the propeller shaft.

If the output of the motor generator 2 and the output of the engine 1are to be used in combination during travel of the vehicle, then theinverter 6 is controlled such that, with the clutch 3 in an engagedstate, an output request signal is sent to the engine ECU 10, and outputfrom the motor generator 2 also can be obtained. The output of the motorgenerator 2 is transmitted to the input shaft 41 of the transmission 4via the power transmission mechanism 5, as illustrated in FIG. 4, andthen passes via the current transmission gear and is transmitted fromthe output shaft 42 of the transmission 4 to the propeller shaft 49,together with the output supplied from the engine 1 via the clutch 3.

When the vehicle is braking, provided that it is possible to storecharge in the accumulator element 7, the inverter 6 is controlled insuch a manner that the motor generator 2 is caused to generateelectrical power from the regenerated braking force which accompaniesthe braking action. The rotation of the vehicle wheels is transmittedfrom the propeller shaft, via the output shaft 42 of the transmission 4,to the input shaft 41 thereof, and then via the power transmissionmechanism 5, to the input/output shaft 21 of the motor generator 2, asillustrated in FIG. 5. Thereby, regenerated electricity is created bythe motor generator 2 and this electrical power passes via the inverter6 and is used to charge up the accumulator element 7. In other words,the energy of the vehicle when decelerating is converted to electricalenergy by the electrical generation process of the motor generator 2 andis recovered in the accumulator element 7. The shortfall in the brakedemand amount can be made up by braking force from electronicallycontrol brakes (not illustrated), or the like.

When charging up the accumulator element 7 whilst the vehicle isstationary, the clutch 3 is engaged with the transmission 4 set toneutral. As illustrated in FIG. 6, the rotation of the engine 1 istransmitted from the clutch 3 to the input shaft 41 of the transmission4, the power transmission mechanism 5, and the input/output shaft 21 ofthe motor generator 2. Consequently, the motor generator 2 generateselectricity due to the output of the engine 1, and this electrical powercharges up the accumulator element 7.

In order to charge up the accumulator element 7 when the vehicle istravelling under the output of the engine 1 only (see FIG. 3), the motorgenerator 2 is caused to operate as an electric motor. As illustrated inFIG. 7, the output of the engine 1 is transmitted via the clutch 3 tothe input shaft 41 of the transmission 4, and then transmitted via theoutput shaft 42 of the transmission 4 to the propeller shaft 49, as wellas being transmitted via the power transmission mechanism 5 to theinput/output shaft 21 of the motor generator 2.

Although the hybrid ECU 20 generates the required driving force by meansof the motor generator 2 only, by disengaging the clutch 3, when thevehicle is accelerating or running as described above, if the amount ofelectrical charge stored in the accumulator element 7 has declined, thenit causes efficient operation to be performed by adding the output ofthe engine 1 to the driving force.

FIG. 10 is a flowchart for this control procedure, which is executed atprescribed control intervals in the hybrid ECU 20.

At step 11, it is determined whether or not the amount of electricalcharge stored in the accumulator element 7 is at or below a prescribedvalue. If the result of this judgement is “no”, in other words, if theamount of accumulated charge is sufficient, then the procedure advancesto step 12, and the vehicle is driven by means of the output of themotor generator 2 only, with the clutch 3 in a disengaged state. In thiscase, the inverter 6 is controlled in such a manner that an outputcorresponding to the amount of operation of the accelerator is obtainedfrom the motor generator 2.

In step 11, if the accumulated charge is at or below the prescribedvalue, then the procedure advances to steps 13-16.

In step 13, the clutch 3 is engaged to assume a state wherein power canbe transmitted from the engine 1. Thereupon, at step 14, the outputdistribution ratio of the engine 1 and the output distribution ratio ofthe motor generator 2 are determined from the map in FIG. 9, on thebasis of the accumulated charge in the accumulator element 7.

This map specifies distribution ratios for the output of the engine 1and the output of the motor generator 2, taking the accumulated charge(SOC) in the accumulator element 7 as a parameter. The greater theaccumulated charge, the greater the output distribution of the motorgenerator 2, and the smaller the accumulated charge, the greater theoutput distribution ratio of the engine 1.

At step 15, the actual output of the engine 1 and output of the motorgenerator 2 are determined on the basis of the distribution ratios thusdetermined and the current amount of operation of the accelerator.Thereupon, at step 16, an output request signal corresponding to thedistributed output of the engine 1 is sent to the engine ECU 10, and theinverter 6 is controlled in such a manner that the distributed output isobtained from the motor generator 2.

In this way, if the accumulated charge (SOC) in the accumulator element7 is sufficient, then the vehicle is accelerated or driven by means ofthe output of the motor generator 2 only, with the clutch 3 in adisengaged state.

On the other hand, if the electrical power is consumed by the drivingoperation of the motor generator 2 and the amount of accumulated chargehas declined to a prescribed value or below, then the clutch 3 isengaged and supplementary output is provided from the engine 1, therebymaking it possible to expand the operational range of the motorgenerator 2 whilst satisfying the required driving characteristics ofthe vehicle. As the accumulated charge declines, the output load on themotor generator 2 is reduced, and hence the accumulator element 7 isprevented from discharging completely.

In an operational state where the vehicle is being driven by the outputof the engine 1 (see FIG. 3), a gear change operation is performed bythe gear shift actuator 43 on the basis of a gear change operationsignal from the change lever unit 23 which generates a gear positioncommand corresponding to the position of the change lever for changinggear operated by the driver, but since the friction and inertia of thepower transmission mechanism 5 and motor generator 2 act upon the inputshaft 41 of the transmission 4 in this situation, there is a great loadon the synchro mechanism during gear changing, and the gear change time(synchro time) becomes long.

Therefore, in this invention, in order to shorten the gear changingoperation, the hybrid ECU 20 controls the rotation of the input shaft 41by means of the motor generator 2 during gear changing, therebyassisting the synchro operation of the transmission 4.

This control operation is now described with reference to the flowchartin FIG. 8.

Firstly, in step 1, it is determined whether or not a gear changecommand (change of gear position command) has been issued, on the basisof the gear position command from the change lever unit 23. If theresult of this judgement is “no”, then the procedure advances to END.

If the judgement at step 1 is “yes”, in other words, if a gear changecommand has been issued, then the processing in step 2-step 8 isperformed, sequentially.

In step 2 and step 3, the clutch 3 is disengaged and the transmission 4is set to neutral (out of gear).

In step 4, a target rotational speed for the input shaft 41 of thetransmission 4 is determined from the target gear ratio corresponding tothe gear position command of the change lever unit 23 and the outputrotation speed of the transmission 4 (detection signal from the rotationsensor 44).

Thereupon, in step 5, the rotation of the motor generator 2 iscontrolled in such a manner that the rotational speed of the input shaft41 of the transmission 4 (as determined on the basis of the detectionsignal from rotation sensor 54) matches the target rotational speed.

In step 6, it is determined whether or not the rotational speed of theinput shaft 41 of the transmission 4 comes within the synchronizationrange corresponding to the target rotational speed. If the result ofthis judgement is “yes”, then the procedure advances to step 7 and step8, wherein the transmission is put into the target gear and the clutch 3is engaged, whereupon, after engagement of the clutch 3, the rotationalcontrol of the motor generator 2 is terminated.

In this way, in gear change control of the transmission 4, bycontrolling the rotation by means of the motor generator 2, therotational speed of the input shaft 41 of the transmission 4 can be madeto converge rapidly to the synchronization range corresponding to thetarget rotational speed, thus allowing major advances to be made inshortening the synchro time and reducing the load on the synchromechanism.

Next, the control for engaging and disengaging the second clutch 60interposed between the motor generator 2 and drive mechanism 5 isdescribed.

FIG. 11 is a flowchart for controlling the second clutch, which isexecuted at prescribed control intervals in the hybrid ECU 20.

In step 21, it is determined whether or not there is a motor generator 2drive request. If the result of this judgement is “yes”, then theprocedure advances to step 22, and the second clutch 60 (motor clutch)is engaged. At step 23, the motor generator 2 is driven and caused toproduce output rotation.

The motor generator 2 drive request is not limited to cases where thetransmission 4 is performing a gear change operation as described above,but rather is also output, for instance, when the vehicle is to bedriven by the aforementioned motor generator 2 alone, when the vehicleis to be driven by a combination of the engine 1 and the motor generator2, when electrical power is to be generated by driven the motorgenerator 2 by means of the engine, or when the motor generator 2 is tobe caused to generate electrical power in order to regenerate thekinetic energy of the vehicle when decelerating.

On the other hand, when there is no drive request, in other words, whenthe judgement at step 21 is “no”, then at step 24, the second clutch 60is disengaged.

In this way, by disengaging the second clutch 60 in advance whenoperation of the motor generator 2 is to be halted, the load on thedrive system is reduced in accordance with the inertial weight andfriction of the motor generator 2, when the vehicle is travelling underthe output of the engine 1 alone, and hence it is possible to promoteimproved fuel consumption of the engine 1. Furthermore, when performinggear change operations of the transmission 4 according to the driver'soperations, by engaging the second clutch 60, it is possible to assistthe synchro operation by means of the motor generator 2.

It is also possible for the second clutch 60 to be interposed betweenthe input shaft 41 of the transmission 4 and the power transmissionmechanism 5.

INDUSTRIAL APPLICABILITY

The present invention is a parallel hybrid drive system which can beused as a drive source for a vehicle.

1. An improved hybrid system for a vehicle that includes an enginehaving an output shaft, a transmission device for changing the speed ofrotation of an input shaft thereof and transmitting said rotation tovehicle wheels via an output shaft thereof, a clutch forengaging/disengaging the output shaft of the engine with/from the inputshaft of the transmission device, a rotational electric device servingas an electric motor and an electric generator, a power transmissionmechanism for coupling an input/output shaft of the rotational electricdevice with the input shaft of the transmission device, and anaccumulator element for accumulating electrical power supplied by therotational electric device, wherein the improvement comprises: means fordetermining gear change instructions for the transmission device; meansfor disengaging the clutch when a gear change instruction is determined;and means for controlling rotation of said rotational electric device,transmitted to the input shaft of said transmission device and geareddown by said power transmission mechanism, in such a manner that therotational speed of the input shaft of the transmission device assumes atarget rotational speed required for the gear changing operation.
 2. Theimproved hybrid system for a vehicle according to claim 1, wherein saidcontrol means determines a target rotational speed for the input shaftof the transmission device from the target gear based on the gear changeinstruction and the rotational speed of the output shaft of thetransmission device, and controls the rotational speed of saidrotational electric device in such a manner that the rotational speed ofthe input shaft of the transmission device approximately matches thistarget rotational speed.
 3. The improved hybrid system for a vehicleaccording to claim 1, wherein a second clutch is interposed between saidrotational electric device and the power transmission mechanism, saidcontrol means causing the second clutch to be disengaged when there isno drive request for said rotational electrical device.